feat(fleet): native Mosaic backlog on @mosaicstack/db (atomic claim + TTL) (#657)

packages/db/drizzle/0011_bitter_gateway.sql

@@ -0,0 +1,22 @@
+CREATE TYPE "public"."backlog_status" AS ENUM('ready', 'claimed', 'blocked', 'done');--> statement-breakpoint
+CREATE TABLE "backlog" (
+	"id" text PRIMARY KEY NOT NULL,
+	"title" text NOT NULL,
+	"body" text,
+	"phase" text,
+	"priority" integer DEFAULT 0 NOT NULL,
+	"status" "backlog_status" DEFAULT 'ready' NOT NULL,
+	"depends_on" jsonb DEFAULT '[]'::jsonb NOT NULL,
+	"claim_owner" text,
+	"claim_ttl_seconds" integer,
+	"claimed_at" timestamp with time zone,
+	"attempts" integer DEFAULT 0 NOT NULL,
+	"idempotency_key" text,
+	"acceptance" jsonb,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"updated_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+CREATE INDEX "backlog_status_priority_idx" ON "backlog" USING btree ("status","priority");--> statement-breakpoint
+CREATE INDEX "backlog_status_claimed_at_idx" ON "backlog" USING btree ("status","claimed_at");--> statement-breakpoint
+CREATE UNIQUE INDEX "backlog_idempotency_key_idx" ON "backlog" USING btree ("idempotency_key");